1. Field of the Invention
This application relates generally to fiber-optic sensors, and more particularly, to fiber-optic gyroscopes.
2. Description of the Related Art
Early experimental demonstrations of the fiber-optic gyroscope (FOG) were obtained using a laser for the optical source. See, e.g., R. A. Bergh, H. C. Lefèvre, and H. J. Shaw, “All-single-mode fiberoptic gyroscope,” Optics Letters, vol. 6, no. 4, pp. 198-200 (1981). Shot-noise-limited sensitivity for the FOG was expected (see, e.g., H. C. Lefèvre, “The Fiber-Optic Gyroscope,” Artech House, Inc., Norwood, Mass. (1993)), but it was actually observed that the sensitivity was dramatically deteriorated by backscattering in the optical fiber (see, e.g., C. C. Cutler, S. A. Newton, and H. J. Shaw, “Limitation of rotation sensing by scattering,” Optics Letters, vol. 5, no. 11, pp. 488-490 (1980)). The replacement of the laser by a superfluorescent source (SFS) (see, e.g., K. Böhm, P. Marten, K. Petermann, E. Weidel, and R. Ulrich, “Low-drift fibre gyro using a superluminescent diode,” Electronics Letters, vol. 17, no. 10, pp. 352-353 (1981)) offered a dramatic reduction of this backscattering-induced noise, along with a reduction of other sources of noise due to the Kerr effect, polarization fluctuations, and the Faraday effect.